Conventionally, xerostomia, called dry mouth, is generally considered to be developed, for example, by systematic illness such as diabetes or renal disease, mouth breathing or smoking, side effects of medicine or treatment, salivary gland disease, central or peripheral nervous disorder, or psychological stress. Xerostomia is often found especially in the elderly. It has been reported that approximately 40% of the elderly suffer from xerostomia.
In Japan, starting with the research of “About xerostomia in the elderly and the physical properties of saliva” in Comprehensive Research Project on Longevity Science by Ministry of Health, Labor and Welfare in 2001 to 2003, various researches have been made, for example, on actual conditions of xerostomia in the elderly and the effectiveness of oral care for the prevention of aspiration pneumonitis. As a result of this, active oral care systems have been introduced, for example, in the National Cancer Center which practices advanced cancer therapy and palliative care. In the revisions on medical treatment fees in fiscal year 2012, the “perioperative oral management fee for cancer patients” has been introduced into insurance based on these systems.
It is important for oral care to measure intraoral moisture accurately. In recent years, an intraoral moisture measuring device including a capacitance type sensor is increasingly used (see Patent Literature 1, for example). For such a capacitance type intraoral moisture measuring device, a moisture amount in mucosa is measured on the basis of a change in capacitance between two electrodes. Therefore, the sensor unit needs to be abutted against a measurement site with a suitable pressing force (load). Thus, when a user is inexperienced in using the intraoral moisture measuring device, there is a risk of producing variations in the measurement result.
As a countermeasure against such a problem, a technique has been proposed in which a sensor is disposed in a slider, which is biased in a pressing direction by a spring, in a skin moisture measuring device, for example, and the magnitude of a pressing force is determined on the basis of a travel distance of the slider (see Patent Literature 2). Also, another technique has been proposed in which a sensor holding structure, capable of easily deforming, is disposed on the rear side of a sensor in an intraoral moisture measuring device, so that the direction of the sensor can be freely changed when being pressed (see Patent Literature 3).